U.S. Pat. No. 7,588,724 (application Ser. No. 11/043,510) and U.S. Pat. No. 7,749,770 (application Ser. No. 12/462,810), and U.S. Pat. No. 7,771,655 (“the '655 patent”) (application Ser. No. 11/485,743), all entitled “Mechanical Device For Mixing A Fluid Sample With A Treatment Solution,” the disclosures of which are all hereby incorporated herein by reference, describe two part devices for mixing a blood sample with a treatment solution prior to release of the treated sample into a fluid analyte meter. Although very useful, a disadvantage of these systems is that, despite the disclosed features, it can be difficult to control pressurization in the devices such that a correct sample volume is delivered to the test cartridge.
For example, these known blood sampler devices often cause a sudden change in the resistance force profile felt by a user while inserting a blood collector into a sampler body, known as the “double pop” sensation. This sudden change, or “jump,” in the resistance force felt by a user often causes users to prematurely stop inserting the blood collector into the sampler body in such known devices, which can result in a lower volume of blood/testing liquid mixture to be dispensed from blood collector into testing strip for an analyte meter or the like. The “double pop” phenomenon of the blood collector and blood sampler body disclosed in the '655 patent is graphically illustrated by the curve in FIG. 8 labeled “Prior Art”. FIG. 8 plots the insertion force required to insert the blood collector into the sampler body versus the distance the sample collector is provided within the sampler body. More specifically, in this known example, the average extension is the distance the portion of the blood collector used to create a seal with the blood sampler passes the seal ring on the blood sampler body. The continuous line identified as “Prior Art” shows the presence of two peaks or apexes in the curve. The first peak occurs when the sealing portion of the blood collector is approximately 0.45 inches past the seal ring in the blood sampler body. At this point, approximately 2 Newtons of force is required to insert the blood collector. The second peak occurs when the sealing portion of the blood collector is approximately 0.45 inches past the seal ring of the blood sampler body. At this point, approximately 12 Newtons of force is required to insert the blood collector into the blood sampler body. However, it is the sharp drops or jumps in the curve immediately following the two peaks, i.e., at an average extension of approximately 0.50 and 0.64 inches, that represent the “double pop” sensation or the feedback felt by a user. The first jump or drop in the resistance force profile occurs at approximately 0.50 inches. Because of the premature drop in force required to insert the sealing portion of the blood collector into the blood sampler body, users are improperly led to believe that the blood collector is fully inserted into the sampler body. It is not until the second drop, at approximately 0.64 inches, that the blood collector is fully inserted into the blood sampler. This point represents the point at which no further force can cause the blood collector to be further inserted into the blood sampler.
Reducing or eliminating this sudden jump in the resistance force profile, and therefore the “double pop” sensation, could reduce or eliminate the likelihood of user error in using a blood sampler device. In this regard, a reduction or elimination of user error can increase the consistency in the volume of blood/testing liquid mixture to be dispensed from blood collector into testing strip. Such an increase in the volume of blood dispensed can facilitate more consistent and/or more accurate test results.